Well, here are a few things:
1) That OS X installation disk (10.6), will only install Snow Leopard for your 2009 MBP
You cannot use that disk for OS X installs on other machines
2) Generally, the applications disk is nearly useless. Your milage may vary, but I've never, ever used them.
3) Obviously your external drive (USB you say?) will have to have enough space to boot the
installation process. I'd recommend 8+ GB if you will actually use this thing. However, you will only need a usb drive as large as the disk image file that we will create later on.
So, lets get started. There are probably guides out there that have more comprehensive answers than this, but I digress.
You need to use Disk Utility for the following steps. It should be in your Utilities folder. Put the OS X install disk into your Macbook, while your USB drive is also in the computer.
- Wipe your USB drive, and reformat it as Mac OS Journaled
- Create a disk image of the CD, saving it to your computer's hard drive.
- Once you have created the disk image, it should be on the left pane of the Disk Utility window. Click on it, then select the 'Restore' tab to the right. You will want the Source to be the disk image file (the OS X install disk), and the Target to be the USB drive.
Let me know how it goes!